U.S. Pat. No. 3,485,706 (Evans) discloses hydraulically needling fibrous webs to produce textile-like nonwoven fabrics. These fabrics are often referred to as spunlaced fabrics and are commercially available from E. I. du Pont de Nemours & Company under the trademark "SONTARA". The hydraulic needling process calls for imparting high energy water jets (i.e., between about 200 to 3,000 psi) to a fibrous web to entangle the web and produce a spunlaced fabric.
In FIG. 40 of Evans, a continuous commercial process is depicted wherein the spunlaced fabric is subsequently dewatered by one or more squeeze rollers, dried, and ultimately collected on a windup roll. After a predetermined amount of spunlaced fabric is collected on the windup roll, the fabric is doff cut by windup knives so that the roll can be prepared for shipping and handling.
In the past, windup knives have been used for cutting relatively lightweight (i.e., less than 2.0 oz/yd.sup.2) polyester or polyester/woodpulp spunlaced fabrics during windup roll doffing. These windup knives typically consist of one or more blades that are tensioned across the fabric in order to cut individual fibers across the width of fabric. Typically, insufficent web tension is developed across the knife blades to produce consistent, clean cuts. The problem becomes even worse when aramid fiber (e.g., "KEVLAR" and "NOMEX" commercially available from E.I. du Pont de Nemours and Company) or heavyweight polyester fiber spunlaced fabrics (i.e., greater than 2.0 oz/yd.sup.2) are collected on the windup roll. Experience has demonstrated that windup knives are unable to consistently cut these sorts of spunlaced fabrics during windup roll doffing. In fact, not only are such fabrics difficult to cut, they also tend to accelerate knife blade dulling. This results in potential safety and quality problems since long wound-in tails can occur from ineffective cutting at doff.
Clearly, what is needed is an apparatus and method for cutting various nonwoven fabrics which do not have the deficiencies inherent in prior art. In particular, the apparatus should be able to cleanly and consistently cut both lightweight and heavyweight nonwoven fabrics, in particular spunlaced fabrics, even if the fibers making up those fabrics are relatively stiff in nature (e.g., heavyweight polyester fibers or aramid fibers). Other objects and advantages of the present invention will become apparent to those skilled in the art upon reference to the attached drawings and to the detailed description of the invention which hereinafter follows.